Electrostatic technique for the contacting and mixing of non-miscible liquids



Feb. 17, 1970 F. J. WRIGHT ELECTROSTATIC TECHNIQUE FOR THE CONTACTINGAND MIXINGOF NON-MISCIBLE LIQUIDS Filed Dec. 7, 1967 25:5 25:3 5 8.5:Ewan 1 3 3 S 3 $32 hzmmw FUDOONE L 0w TwmDOI QmmI l nvantor F. J. WrightI Patent Attorney United States Patent O 3,496,100 ELECTROSTATICTECHNIQUE FOR THE CON- TACTING AND MIXING OF NON-MISCIBLE LIQUIDSFranklin J. Wright, Watchung, N.J., assignor to Esso Research andEngineering Company, a corporation of Delaware Filed Dec. 7, 1967, Ser.No. 688,858 Int. Cl. Cg 19/02;B01k J/00; B01f 3/08 U.S. Cl. 208265 4Claims ABSTRACT OF THE DISCLOSURE The instant disclosure is directedtowards a method and apparatus for electrostatically mixing andcontacting liquids. The method is particularly useful for obtaininglarge surfaces of contact between nonconducting liquids such ashydrocarbons with conducting liquids such as caustic or acid solutionsor water. The teachings herein disclose the transferring of electricalcharges to the conducting liquid by passing the same through a metallicnozzle which is connected to a high voltage supply. By using the methodand apparatus of the instant disclosure, an extremely fine dispersion ofthe conducting liquid may be obtained in the nonconducting liquid.

BACKGROUND OF THE INVENTION In many refinery and other industrialoperations which involve the contacting of immiscible or partiallymiscible liquids, the efficiency of the operation depends greatly on thethoroughness of the contacting and mixing of the two phases. The higherthe degree of dispersion of the one phase with the other and the greaterthe degree of agitation, the greater is the contact achieved.

In practice, dispersion has generally been accomplished in the prior artby means of propeller bladed mixers or other mechanical devices, all ofwhich require moving equipment, such as impellers, circulating pumps andthe like. It will be appreciated by those skilled in the art that whenmechanical devices such as propellers are used for stirring and mixing,various associated problems exist. For example, when stirring and mixingin pressure vessels, packing glands for the rotating propeller shaftsare necessary. The use of packing glands often results in associatedundesirable maintenance problems. In addition, moving parts are prone tomechanical failures, particularly in the presence of corrosive solutionswhich may be undergoing processing. Aside from these purely mechanicaland/or maintenance problems, ditficulties still exist in obtainingadequate contacting and mixing of the immiscible or partially miscibleliquids by purely mechanical means.

The novel technique and apparatus for contacting liquids which form thebasis of the disclosure for the present invention is based on the use ofelectrostatic fields and not only can provide equal or better dispersionand agitation than can be obtained by mechanical means but can achievethis without resorting to any moving parts. Thus, servicing andmaintenance are held to a minimum, particularly since all electricalcomponents to be used can be considerably overdesigned at little or noextra cost.

SUMMARY OF THE INVENTION By way of example and obviously not by way oflimitation, the novel electrostatic mixing technique of the instantinvention will be discussed in the environment of an acid washing of ahydrocarbon feed.

The mixing of sulfuric acid with a hydrocarbon is selected as an examplebecause of its importance in processes such as alkylation and also inorder to clearly demonstrate the difference and substantial improvementspresented by the present invention over the prior art, which describesthe use of electrostatic fields to mix liquids (see in this regard U.S.2,884,375).

The prior art teaches that dispersion can be produced by applying avoltage across the boundary between two liquids. This technique islimited, however, to a few special combinations of liquids such as, forinstance, heptane and nitrobenzene or aniline. The technique fails ifone of the liquids is a good conductor of electricity such as caustic oracid solutions or even water. Unfortunately, these are the very types ofliquids which are of the greatest interest in many refinery operations.The reason for the breakdown of the technique with good conductors isthat with a conducting liquid, the boundary between the two liquidsbecomes in essence the electrode and hence only the nonconductinghydrocarbon is subjected to the field.

The present invention on the other hand operates best in these verysituations, i.e., when a conducting liquid is to be dispersed in anonconducting one. If two nonconducting liquids were required to bemixed, considerable improvement in the effectiveness of theelectrostatic technique could be achieved by making one of the liquidsslightly conducting by the addition of a very small concentration of asoluble polar substance capable of enhancing the conductivity ofhydrocarbons. Examples of such additives are bifunctional compounds suchas dinitriles, diamine alkanes, hydroxy nitriles, hydroxy amines, dihaloalkanes, halo-cyano alkanes and also esters of phytic acids.Concentrations of 1 p.p.m. to 0.1% are effective, the preferredconcentrations being in the range of 10 to 1000 p.p.m.

The hydrocarbon is contained within a suitable tank while the acid washsolution is introduced into the hydrocarbon by means of an injectorcomprising a suitably sized electrically conductive nozzle or through aplurality of such nozzles. The injector, which serves as an electrode,is connected to a high voltage power supply, another electrode beingimmersed in the hydrocarbon itself. With the application of a highvoltage from the power supply to the injector, the acid solution issuesfrom the nozzle or nozzles as a very fine mist of droplets. An extremelyhigh contact surface is thus presented to the oil by the acid droplets.Furthermore, since these droplets are charged as they enter theelectrical field between the nozzle or nozzles and the electrode in thehydrocarbon feed, they are greatly agitated.

As will be appreciated by those skilled in the art, the nozzle ornozzles can be made either the positive or the negative electrode, theformation of the dispersed droplets being unafiected by the polarity ofthe field. It was unexpectedly found that AC voltages were equallyeffective. While the voltage necessary to produce these droplets is inthe range of 20 to 30 kilovolts, the resultant currents are quite small(usually less than 10* amps) and thus the power consumed is of a lowmagnitude, being on the order of 1 or 2 watts at the most.

It will be further appreciated that the acid droplets continue to movetowards the electrode in the hydrocarbon and they will eventuallycoagulate in its vicinity. Thus, the equipment operates, in addition toa contacting means, as an electrical coagulator. This, of course,greatly improves the efiiciency of the overall Wash process since itensures that no treating agent (in this case acid) is carried over tothe next processing stage with the treated hydrocarbon feed.

In spite of its apparent simplicity, the instant device and methodproduce a great many advantages over contacting processes used in theprior art. For example, contacting time between the hydrocarbon and theacid used in the above example can be greatly reduced because of thehighdegree of dispersion. Thus, the possibility of undesirable sidereactions leading to sludge formation and acid consumption is reduced.Furthermore, the process can easily be operated under superatmosphericconditions since there is no requirement dictating the use of usuallytroublesome packing glands around rotating shafts. Under such conditionsoxygen may be readily excluded, thereby preventing gum formation and thelike; and, hence problems such as pumping of a gummy acid wash solutionare avoided. It will also be seen that because no moving machinery isinvolved, service factors and maintenance, as "well as the cost ofinitial installation, are all minimized.

Thus, an object of the instant invention is to provide a method andapparatus for the mixing and contacting of nonmiscible liquids orpartially miscible liquids.

Another object of the instant invention is to provide an electrostatictechnique for mixing and contacting immiscible liquids which avoids thenecessity of using mechanical agitation means.

Still another object is to provide an electrostatic mixing andcontacting method and technique which is particularly useful forobtaining large surfaces of contact be tween a nonconducting liquid suchas a hydrocarbon with a conducting liquid such as a caustic or acidsolution of water wherein the technique also operates as an electricalcoagulator.

These and further objects as well as a fuller understanding of theinvention may be had by referring to the following description andappended claims taken in conjunction with the associated drawings.

BRIEF DESCRIPTION OF THE DRAWINGS FIGURE 1 shows schematically a mixingand contacting apparatus according to the teachings of the instantinvention.

FIGURE 2 illustrates a typical acid and caustic washing process to beperformed on a hydrocarbon feed, which process employs the method andapparatus of the instant invention.

DESCRIPTION OF A PREFERRED EMBODIMENT Referring to FIGURE 1 in detailand again using by way of illustration concentrated sulfuric acid and ahydrocarbon as the liquids to be contacted, the apparatus and method ofoperation is as follows:

The hydrocarbon 14 is placed in a suitable container 12. The sulfuricacid (or other conducting liquid) is stored in a suitable vesseldesignated by the reference numeral 2. Vessel 2 has at its lower end ametallic nozzle 4. It will be appreciated by those skilled in the artthat nozzle 4 may take on any number of configurations and is to besized in accordance with the amounts of fluids being handled. Thus, forexample, in small scale laboratory work, this nozzle can be fabricatedof stainless steel hypodermic tubing having a gauge number of 22. As maybe seen in FIGURE 1, the end or tip of noz zle 4 is submerged beneaththe surface of hydrocarbon 14. A suitable high voltage power supply 6,such as a transformer, maintains nozzle 4 at a high potential (withrespect to ground) in the range of from about 1 kilovolt to about 50kilovolts through the lead 8. Another electrode held at a lowerpotential {c.g. ground) is submerged in the hydrocarbon below nozzle 4.It will be understood that in the absence of a voltage across the twoelectrodes 8 and 10, large drops of the sulfuric acid would form at thetip of the nozzle, then break off and slowly sink to the bottom of thevessel 12. However, in the presence of a field, the sulfuric acid issuesfrom the nozzle as a fine mist of droplets of colloidal dimensions. Dueto the existence of the field between electrodes 4 and 10, thesedroplets are violently excited in a random fashion as they traveltowards the submerged electrode 10. Eventually the acid droplets reachthe electrode 10 where they coagulate and fall to the bottom of thevessel 12 as indicated at 16. Thu h q ipment not only serves as acontacting means but also operates as an electrical coagulator. Thiseffect, of course, increases the efiiciency of the overall process sinceit assures that no acid is retained in the hydrocarbon.

In order to disperse the sulfuric acid, electrical charges must betransferred to the acid from the nozzle which is acting as an electrode.This transfer is dependent on the conductivity of the liquid, the natureand extent of the contact between the charged surface of the electrodeand the liquid, the flow rate and the magnitude and type of highvoltage. In this regard polarity of the field is not of sufficientimportance so the nozzle can be made with a positive or the negativeelectrode or it can be attached to an AC power supply. From a practicalpoint of view, the fact that AC is eifective is useful since, ingeneral, equipment to generate high AC voltage is cheaper and less bulkythan high voltage DC power supplies.

Example Using concentrated sulfuric acid and heptane as the liquids tobe mixed, and employing a nozzle made from a stainless steel hyprodermictubing (No. 22 gauge) a voltage of about 20 to 30 kilovolts applied tothe nozzle resulted in a spray angle of over emanating from the tip ofnozzle 4. This angle and the fine mist of sulfuric acid droplets whichformed at the tip of nozzle 4 produced highly satisfactory contactingand mixing of the sulfuric acid with the heptane. While the voltageswere as indicated, the currents measured were quite small (being in therange of about 10- amperes). Thus, the power consumed is normally verylow, being on the order of l or 2 watts at the most.

A flow scheme exemplifying the use of the instant apparatus and methodin acid and caustic washing of a hydrocarbon feed is shown in FIGURE 2.The hydrocarbon feed to be treated is introduced into a tank 12 via theline 11. Two electrodes 20 and 10 are provided within the tank 12.Electrode 20 is in the form of a manifold portion 21, to which areaffixed a plurality of injection nozzles 4. A potential difference isimposed between electrodes 20 and 10 by use of the high voltage powersup ply 6 which is operatively connected to electrode 20. An acidsolution such as H 50 and water contained in tank 2 is pumped via pump32 and the line 34 into manifold 21. As hereinbefore indicated, due tothe high voltage applied to electrode 20, the acid solution issues fromnozzles 4 as a very fine mist of droplets. Thus, an extremely highsurface is presented to the hydrocarbon within the tank 12. Furthermore,as these charged droplets enter the electrical field between the twoelectrodes 20 and 10, they are greatly agitated. Eventually, the aciddroplets 13 move towards the ground electrode 10 where they coagulate,the equipment operating as an electrical coagulator at this juncture.The coagulator acid exits the tank 12 via the line 22. A portion of thismaterial may then be recirculated via the line 24, the remainder exitingthe system via the line 26. An acid make-up line 28 provides additionalacid to the tank 2. It will be appreciated by those skilled in the artthat the coagulation effect above mentioned greatly improves thechiciency of the overall process since it ensures that none of the acidwash is carried over to the next, i.e. caustic wash, stage.

The acid 'washed hydrocarbon feed exits tank 12 via the line 38 andenters a caustic wash tank 39. The operation of this portion of theprocess is exactly analogous to the acid wash portion just described.Thus, a caustic wash is contained within the tank 46, which wash ispumped via the line 36 to the manifold portion 21 of electrode 20'. Asbefore, electrode 20- is supplied with a high voltage from a highvoltage power supply 6'. The spent caustic exits tank 39 via the line40, a portion being recycled via the line 44 and the remainder leavingthe system via the line 42. Fresh make-up caustic is supplied to thetank 46 via the line 48. The caustic wash hydrocarbon feed exits thetank 39 via the line 46.

Although the invention has been described with a certain degree ofparticularity, it is to be understood that the present disclosure hasbeen made by way of example and that obviously changes in the details ofconstruction and arrangement of parts may be resorted to withoutdeparting from the spirit and scope of the invention as hereinafterclaimed. It is also to be appreciated that the invention is obviouslynot limited to the acid and caustic washing of a hydrocarbon feed andthat the flow diagram represented in FIGURE 2 is intended to beillustrative in nature.

In view of the above, reference should be had to the following appendedclaims in determining the full scope of the instant invention.

What is claimed is:

1. A method of forming a dispersion between an electrically conductingliquid with a nonconducting liquid, said conducting liquid being atleast partially immiscible in said nonconducting liquid, which methodcomprises the steps of:

(a) maintaining a body of non-conducting liquid;

(b) maintaining an electrical field in said body of nonconductingliquid;

(c) feeding said conducting liquid to an ejector suspended in said bodyof non-conducting liquid;

((1) maintaining said ejector at a potential of from about 20 to about30 kilovolts with respect to ground potential;

(e) passing said conducting liquid through said ejector whereby saidconducting liquid emanates from the tip of said ejector as a pluralityof electrically charged fine droplets, said droplets being dispersed insaid body of non-conducting liquid under the infiuence of saidelectrical field.

2. The method of claim 1 wherein said conducting liquid is selected fromthe group consisting of aqueous caustic solutions and aqueous acidsolutions and said nonconducting liquid is a hydrocarbon.

3. A method of forming a dispersion between a first normallynonconductive liquid and a second normally nonconductive liquid, saidfirst liquid being at least partially immiscible in said second liquid,which comprises the following steps in combination:

(a) maintaining a body of said second normally nonconducting liquid;

(b) injecting an amount of a soluble polar substance into said firstliquid whereby the conductivity of said first liquid is enhanced;

(c) feeding said first liquid through an ejector suspended in said bodyof said second normally nonconducting liquid;

(d) maintaining said ejector at a potential from about 20 to aboutkilovolts with respect to ground potential;

(e) maintaining an electrical field in said second normallynon-conducting liquid; and

(f) passing said first liquid through. said ejector whereby said firstliquid emanates from the tip of said ejector as a plurality ofelectrically charged fine droplets, said droplets being dispersed insaid body of said second liquid under the influence of said electricalfield.

4. The method of claim 3 wherein the amount of said soluble p'olarsubstance is sufiicient to obtain a concentration of said substance insaid first liquid in the range of from about 10 p.p.m. to about 1000p.p.m.

References Cited UNITED STATES PATENTS 2,033,446 3/1936 Pettefer 2043023,169,915 2/1965 Kennedy 204171 1,565,992 12/1925 Eddy 208187 2,050,3018/1936 Fisher 20'4l85 2,884,375 4/1959 Seelig et a1. 208146 3,309,4133/1967 Ferrara et a1. 208-267 DELBERT E. GANTZ, Primary Examiner G. J.CRASANAKIS, Assistant Examiner US. Cl. X.R.

